Frequency selective electrical device



March 14, 1950 J. P. KINZER FREQUENCY SELECTIVE ELECTRICAL DEVICE 2 Shee-ts sheet 1 Filed June 1 1946 L.P. FILTER lNl ENTOR J. P K/NZEP BV Z V g I AT TORNEV J P. KINZER FREQUENCY SELECTIVE ELECTRICAL DEVICE March 14, 1950 2 Sheets-Sheet 2 Filed June 1, 1946 INVENTOR JPK/NZE/P BV V Z ATTORNEY Patented Mar. 14, 1950 FREQUENCY SELECTIVE ELECTRICAL DEVICE John P. Kinzer, Ridgefield, N. J assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 1, 1946, Serial No. 673,742

11 Claims.

This invention relates to frequency selective electrical devices and more particularly to cavity resonators capable of resonance frequency variation over a continuous frequency range.

An object of the invention is to provide a variable frequency resonator with a minimum of mechanism.

Another object of the invention is to vary the effective volume of the cavity resonator without the necessity of providing moving end walls with their cumbersome supports and guides.

A further object of the invention is to enable matching characteristics of a lot of cavity resonators which differ in their internal dimensions without introducing a factor of dissymmetry in the resonators.

Another object of the invention is to produce relatively low frequency oscillations and to stabilize their frequency by space resonators which are of moderate dimensions.

In accordance with one embodiment of the invention a cavity resonator in the form of a wide circular cylinder has as its interior circular wall the surface of a coiled flat spring which may be withdrawn from the cylinder through a tangential slot to increase the diameter of the resonator thus reducing the natural resonance frequency of the resonator. As the spring is withdrawn it may b introduced through a tangential slot into an adjacent similar cylinder which may serve merely as a magazine or storage device or may, itself, constitute a second resonator, the interior diameter of which decreases as that of the first resonator increases. An electron discharge device may be associated with the first resonator to constitute an oscillator. If both cylinders are resonators provided with electron discharge devices the whole system may be used to produce beat frequency oscillations which maybe rapidly varied in frequency since the frequency of one resonator increases as that of the other falls. In order to insure matching of the characteristics of two resonators having different interior diameters an additional coiled spring may be introduced into the resonator with the larger diameter to reduce its diameter effectively to that of the diameter of the smaller resonator.

In the drawing:

Fig. l is a section of apparatus and a schematic diagram of associated circuits of a system constituting one embodiment of applicants invention in which beat frequency oscillations are produced;

Fig. 2 is a sectional view along the plane passing through the dash line 2--2 of Fig. 1; and

Fig. 3 illustrates a modification of the resonance chamber of Figs. 1 and 2.

Referring to the drawing, a two-part resonant cavity [0 of cylindrical'conformation having a short length and a relatively large diameter comprises a substantially closed resonance chamber having an interior surface of highly electrically conducting substance such as copper or silver. The end walls of the cylindrical structure are provided with central apertures having inwardly extending peripheral portions I I and 12 which serve as seats for the outwardly extending metallic flanges l3 and M respectively of an electron discharge tube I5 which may be of the type manufactured by Western Electric Company, Incorporated and designated as 707A. The discharge tube includes a heater I6, a cathode H, a shielding or guard ring [8 which may be suitably negatively polarized to collimate the beam from the cathode I1 and a highly positiv cylindrical anode l9 integral with the flange Hi. The cathode l1, collimator l8 and anode l9 constitute an electron gun. Extending across the outer end of the anode I9 is a screen 20 which faces a closely adjacent screen 2| supported by an annular electrode 22 which is integral with the flange [3. The peripheral electrode 22 extends outwardly through the dielectric wall 23 of the tube l5 and is accordingly maintained electrically insulated from the remaining electrodes. A repeller or tar get electrode 24 is supported by a stem 25 passing through the end wall of the tube l5 opposite the electron gun. By virtue of the annular gap between the inner margins of the peripheries of the screen 20 and the screen electrode 2| the electric field within the resonator It may interact with the electron stream passing from the electron gun across the gap toward the repeller electrode 24. To velocity-vary the stream in such manner as to accelerate the electrons when the field within the resonator makes the potential of the seat I! positive with reference to the seat l2 to retard the electrons when the potential of the seat II is negative with reference to the seat [2, the electron stream of the electron discharge tube is coupled to the electromagnetic field within the resonator III by virtue of the mutually shared space between the screens 20 and 2|. The discharge tube l5'together with the resonator l0 and the energizing sources with their external circuits, not shown, constitute a reflex or repeller oscillator of the type disclosed at Fig. 3 of the article Reflex Oscillators by J. R. Pierce, published at page 113 of the Proceedings of the I. R. E., February 1945. The resrive the difference frequency .or beat .frequency onator I serves as the frequency determining element of the oscillator. Reference is made to that article for a description of the external polarizing circuits of the present invention and of the theory of operation of such oscillators.

The resonator ID, as indicated by the sectioning of the outer wall in Fig. 2, consists .of .two semicylindrical :Estructures, these structures being clamped or held together in any desired manner. It contains a coiled flat metallic spring which resembles a clock spring and tends to remain tightly in contact with the interior cylindrical wall 3| of resonator Ill. The spring 30 is a flexible metallic ribbon made with a slight lateral convexity or concavity in a vmanner -.to give it 115 a slight tendency to straighten itself. .sItiis :just wide enough to fit within the cylindrical resonator without binding. Because 'of itstentlency to straighten, it will hug the inner cylindrical wall of the resonator. The spring may be unwound or .rewound by .a drive .mechanism weonsisting of friction -rollers P132 .and $3.3, .theiormer of which rotatably.mountedion a.shaft..on a support integral with the external -casing .34 .of 'theapparatus and ;the'.latter.of -.which.is .impelled by a stiff leaf .spring Z itowardiroller 3.2 .and .in .contact .with Lthe spring .30. The .outer .end .of the .spring "30 passes irorn the resonator 10 through a itangeritialslot -38 and betweencrollers .32 and .33 and thence in through another .tansgentialslotil "into the linterior of the two part magazine 38 whicnma ibea mere .storagegpace 'for the .unreeled portion ,Q'fspring .30 .or .which may be, vas illustrated, a riduplicate of resonator 0.

"The resonator ,38-may. serve .with-ramassociated electron discharge devicesimilar .to .tube .[5 .as a. second reflex oscillator. For each .of .the (two oscillators .39 and 14.0, Lloop output .couplers M projecting Iinto Tthe .resonator field space :may provide .output .energy itransducers -.associated respectively with the coaxial .ci-rcuits A2 and 43 which are .connected .to .the .input-of a..modu- 'lator orffrequencyconverters-4 designed .-to deor the Ltwo oscillators. 120 ".the .output of -.the modulator M .alaeatifrequency currentrcircuitM -maybe :connected -.through 1 an intermediate .low- ,pass filtericfi .which-may.serve .torestr-ict the transmitted "frequency ..range i130 Ithe difference...)

frequency ,producedLin .thecorrlbiner. onmodulator 4'4. Sinoewthecoiled springjfl in ..one-cavity resonator moves in. such azmanner as ..to increase sthe "frequencyiin .onenesonatorcat' the: samevtimezthat ittlecreases 'thatlintheiother, the .beat frequency varies .very -rapidly. .rIErequency scalibration 0f "the. beat .frequency .oscillator may .bereffected -.by marking itheiportioniof .the- -spring tapesill .which passes ,inifrorit ofithe .window :26 .of-thecasingtfl.

"To,prevent, .pileuprof the..spring..30 .tossucnan extent as to contact with or .interfere with the 'loopcoupler .M, .the inner wallrof therresorrator [0 may The "provided .withan inwardly-projecting circumferential rib '41 which .limits .theramount cf thespring which may the wound into that .particular resonator.

.iIn .order, .to .ccmpensate :for rmanufaeturing variations .in .theresonators it imay be desirable to .provide -means .for insuring that tithe .-init-ial :resonances of all .the resonators rarer alike. This .mayibahadhythe use ofiassecond-eoiled spring A8 similarsto thesspringififl butvverymuchrshorter hand which winds: in such; manner; as ;to interleave .with .the spring .39. :This sauxiliary or ';com- .pensating spring -may be introduced into -theresonator through a tangential slot 49 as shown in Fig. 3. The spring 48 may be supplied with any desired propelling and holding device (not shown) mounted on the exterior of the resonator. The compensating spring may be introduced into the resonator having the larger effective internal diameter .andmay beifixedrin position so as to maintain .initial resonance freguencies of the various resonators alike. This expedient is also of use in single resonator apparatus to adjust the natural resonance frequency of a cylindrical resonator.

It will be apparent that the beat frequency roscillatorrapparatusris relatively compact and is :ireexiromamore elaborate piston or plunger ssupportin vmechanism customarily required in .thecase. of .wide. range tuning of cavity resonators.

What'is claimed is:

11in electrical resonator comprising a closed circular chamber having electrically conducting .rmeans rte-r warying :the frequency sthereof reomprising ;an :electrically conducting dining member within said rchamber zand acontiguous .to said Wa.1l's,::said iwalls .having :a slot, and .rmeans forawithdrawing. said imemberslin 2a egradual .:marmerz.throughssaid slot.

2. A pair of electrical resonators Leach-room- 'ipris'm'g an electrically :resonant whamber :having "Wallis-10f relectrically rconducting imaterial, 1a wall :of reach rofssaidrchambers'zhaving sslots awh-ichina'e aligned with seach sothe-r, tmeans Mai-tying uthe ifrequency (of :said :ehambers coppnsitely comprising a 'ffiexible telectrically :condu'ctirrg spring .-ribbon extending ct-hrough said islets rand z'terrriinat- ,;ing -:a mall zin reach sch-amber, rand imeans if'Ol withdrawing said ribbon gradually from one chamberandintroducing? it into the other.

in :'combination, ftwo miicrowave oscillation generators each comprising a frequency determining chamber resonator "hawking an electron beam traversing? it anii iriteracting with the iield thereo'f, and movable -tuning 'means simultaneously extendin'g irito eachof said chambers *for varying ftheir respective resonance ifrequenies in oppesite sense.

*4. Thecombination in' accordancewvith'wclaimt, characterized in this, 'that the resonance frequency or "one 'chamber "is *irrcrea-sed "as that :of tthe'other is-decreased.

5. *A 'tcavity -resonator comprising :a "closed icylindrical conducting chamber andmeansfontunling: saitl resonator 'comprisingwfiavspring coiled "rtherewithin fitting .c'losely against the interior cylindrical wallandvariably 'extensivelength withinsaid "chamber which varies the natural resonance-frequency oflsaid-Jesonator.

.6. *Apair'of similar cavity.rescnators'eachcomprising 'a fixed .gcylindrical gehamber and .having electrically conduct n Walls and "means .for

matching -their ,resonance frequencies comprising. av coiledspringtiitting tightly against. the .wall er Lthe chamberihaving-.thelower natural res- ,onance frequency, 4 said spring having a length .afdiustablelto increaselthe.resonanceifrequency.of

.the chamber to ,.equalithe natural resonance "frequencies ofthesecon'dchamber.

'7. A cavity resonator ofhigh JQcompiiSihg a :closed -.ooncl.uctive cylinder, tuning. means .there- .for comprisinga. coiled metalx membenin .closefitting. contact withinsaid r cizlin'derandadapted .to-bea'withdrawn ,from ;said navity .to .varyithe internal diameter thereof, and means .for..ex- .citingssaid resonator; into electrical roscillation.

: 8..ThesStr11'0tureDf claim 17, where ssaidmemher is a flat spring and said exciting means is an electron beam traversing said resonator.

9. The structure of claim 3, wherein said tuning means comprises a flexible, conductive spring terminating in a coil in each chamber, separate electron beams for exciting each chamber into electrical oscillation, and means for deriving beat frequency oscillations over an extended frequency range from said chamber oscillations.

10. A pair of similar cavity resonators each comprising a fixed cylindrical chamber having electrically conducting walls, each of said walls having tangential slots, variable tuning means for said chambers comprising a spring-like mem- User the ends of which extend respectively 15 through said slots into each of said chambers and coil therewithin and means for simultaneously withdrawing a portion of said member from one of said chambers to decrease the resonance frequency thereof and introducing a like portion into the other of said chambers to increase the resonance frequency thereof.

11. The structure of claim 10 including second and third spring-like members extending separately through said slots into each of said chambers and coiled therewithin interleaving with portion of said first member within each of said chambers to adjust separately the initial resonance frequency of each of said chambers.

JOHN P. KINZER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,666,077 Victor Apr. 17, 1928 2,044,413 Weyrich June 16, 1936 2,240,452 Wolfskill Apr. 29, 1941 2,245,627 Varian June 17, 1941 2,331,892 DeLisle Oct. 19, 1943 2,396,044 Fox Mar. 5, 1946 2,405,277 Thompson Aug. 6, 1946 2,410,109 Schelleng Oct. 29, 1946 2,411,289 Mouromtseff Nov. 19, 1946 

